The present invention relates to an electromagnetic wok, more particularly, to an electromagnetic wok which is a cooker with a cyclic watercooling system applied in big restaurants, camps or factories. The activating power for the instant invention is under 30 KW.
FIG. 1 shows the magnetic figure of prior art. Accordingly, conventional electromagnetic wok has a plurality of circular induction coil 2, on which a insulation layer 1 is disposed as shown in FIG. 1. A wok body 1A is disposed on the insulation layer 1. The circular induction coil 2 generates magnetic figure 2B to heat the wok body 1A. However, the induction coils 2 of conventional electromagnetic wok is adapted the manner of air cooling. Thus, the longer conventional electromagnetic wok is used, the higher the temperature raises. And this causes the resistant value to raise and leads to the energy loss. Hereunder are examples and calculations taken from a regular conventional electromagnetic wok of 1000 watts.
1. The heating efficiency of the best performance is 90%, and the best performance results from no superfluous objects disposed between the wok body 1A and the insulation layer 1. In addition, the thickness of the insulation layer 1 is at most 2 mm (millimeters).
2. The magnetic conductivity of the wok metal must be good. If the metal of the wok body is made of galvanized iron, the heating efficiency of the performance is approximately 80%.
3. The thickness of the wok bottom should be at least 4 mm. If so, the heating efficiency will be kept. If the thickness of the wok bottom is under 1 mm, the heating efficiency of the performance will be reduced under 80%.
To average the above-mentioned factors, the heating efficiency of the performance is approximately 80%. In the 20% loss, the induction coils shares 95% of the loss. In other words, the induction coil is responsible for 19% total power loss. Calculations are described as follows.
The induction coefficient of the iron wok is 0.3. We have power of the induction p=1000 w.times.0.9 (real induction power)=900 w (watts).
Therefore, the virtual induction power of the induction coil equals to p.div.0.3=3000 VA (volt-ampere). If the induction coil has 100 V current, then EQU 3000 VA.div.100 V=30 A.
The inductive reactance of the induction coil is EQU R/X.sup.L =0.11.OMEGA.
and the loss is w=I.sup.2 .times.R=99 w, EQU 99 w.div.1000 w=9.9%,
therefore the efficiency is 90.1%.
When the wok is made of galvanized iron, the induction coefficient is 0.1333. The real induction power p=3000 VA.times.0.1333=399.9 w. The loss is 99 w.div.(399.9+99 w).apprxeq.20%.
If the wok is continuously used, the temperature of the induction coil will be raised to 45.degree. C. And the resistant value is 4.44/1000 times the temperature index of resistor per degree. 4.44/1000.times.45.degree. C.=39.96/200, and this means 20% , therefore EQU 99 w.times.(1+20%)=120 w.
Accordingly, conventional air-cooled induction coil causing the energy waste is apparent. If the power is raised sixteen times to deal with rapid heating and cooking of the large quantities of food stuff, the power is raised to be sixteen kilo-watts, the voltage is multiplied by four, and the current should read 120 amperes. Due to the formula p=I.sup.2 .times.R, and the inductive reactance of the induction coil is R/X.sup.L =0.11.OMEGA. if the original induction coil is used, thereby p=120 A.times.120 A.times.0.11.OMEGA.=1.584 KW. The heat we obtain will surely destroy the conventional air-cooled induction coil.
The watercool electromagnetic induction heating wok overcomes this shortcoming by keeping its induction coil ambient temperature, and thus, its security is granted and its life is prolonged.